Probably pretty good, the spec is plus/minus 3dB from 29Hz-100Hz, with a long term output of 139dB. IIRC however at least the bandwidth spec was based on the intended pack of 4 to create a large horn with a 60"x60" face, 45" deep, weighing 1000lbs. They were not really intended to be used singly.

I sold the Labs because I didn't like the form factor and lack of handles. BH760 has a more appealing shape and handles.

I'm putting together an old EAW rig for fun. Got 4+4 KF650Isr/Sb600 and 8 KF750 for cheap. The plan for 2017 is to paint the KF750 and replace a pair of drivers. KF650/SB600 was redone this year, swapped a couple of drivers and modified them to NL8.

I need subs for the KF750s some day, no hurry. I can rent for the very few shows this rig will do in 2017.